The standardization of a Long Term Evolution (LTE) system which is a wireless communication system (Rel. 8 and Rel. 9) of 3.9G mobile phones has been completed, and the standardization of LTE-Advanced (LTE-A) (also referred to as IMT-A) system (from Rel. 10 onwards) which is an enhancement of the LTE system as one of 4G wireless communication systems has been currently performed.
The LTE system or the LTE-A system needs to cope with a rapid increase in data traffic, and the introduction of a technology for improving a peak data rate or spectral efficiency and the reservation of frequency resources are important issues. In the LTE system or the LTE-A system so far, the use of a frequency band referred to as a so-called licensed band permitted for use from a country or a locality in which a radio communication operator provides services is assumed, and there are limitations of an available frequency band.
Thus, the provision of the LTE system (referred to as LTE-U) that uses a frequency band referred to as a so-called unlicensed band which does not require the permission for use from country or locality has been recently discussed (see NPL 1). In the LTE-A system, a carrier aggregation (CA) technology which uses one system band of the LTE system as a component carrier (CC) (also referred to as a serving cell) and performs communication using a plurality of CCs has been adopted. A method of applying this CA technology to the unlicensed band and utilizing the unlicensed band has been expected as one method for coping with the rapid increase in data traffic.
It is considered that a frequency band (for example, a frequency band which is allocated for television broadcasting but is not used by the locality) called a white band (white space) that is not used in reality in order to prevent the crosstalk between frequencies or a shared frequency band which is exclusively allocated to a specific operator but is expected to be shared between a plurality of operators in the future is used for cellular communication in the future in addition to the unlicensed band.